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    <title>Document</title>
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    <script>
        //数组  arr是对象 Array是类
        // var arr = new Array()   //从array类创建一个具体对象
        // var arr = ["a", 1, null, false]
        // //console.log(arr[arr.length - 1])最后一个元素
        // for (var i = 0; i < arr.length; i++) {
        //     console.log(arr[i])
        // }





    </script>
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